Magnet structure for cylindrical gasfilled crossed-field diodes



- June 4, 1968 G. BOUCHER 3,387,165

MAGNET STRUCTURE FOR CYLINDRICAL GAS-FILLED CROSSED-FIELD DIODES Flled April 26, 1966 2 Sheets-Sheet l INVENTOE. GILBEET TSoucHeR 3,387,165 -FILLED G. BOUCHER MAGNET STRUCTURE FOR CYLINDRICAL GAS June 4, 1968 CROSSED-FIELD DIODES 2 Sheets-Sheet 2 Filed April 26, 1966 luvs/V7042, GILBERT Baum-IE2 BY MKNEY United States Patent 3,387,165 MAGNET STRUCTURE FOR CYLINDRICAL GAS- FILLED CROSSED-FIELD DIODES Gilbert Boucher, Paris, France, assignor to CSF- Compagnie Generale de Telegraphie Sans Fil, a corporation of France Filed Apr. 26, 1966, Ser. No. 545,486 Claims priority, application France, May 4, 1965, 15,675 4 Claims. (Cl. 313156) This invention relates to gas-filled diodes of the type in which the electrons propagating from the cathode to the anode are submitted to the combined action of crossed electric and magnetic fields, and it is particularly concernexl with diodes having a cylindrical structure in which the anode occupies the axial position while the cathode is a cylinder surrounding the anode. More particularly, the present invention relates to diodes of the type specified, in which the distribution of the magnetic field in the interelectrode space is rendered heterogeneous so that the component thereof in the direction perpendicular to the electric field is variable and increases towards the cathode surface.

In a known embodiment of diodes of this type the magnetic field has an axial component whose desired intensity variation is achieved by producing the magnetic field with the aid of an electro-magnet, which comprises a winding that surrounds the cathode cylinder and has a small length in comparison with the length of the cylinder. These diodes present the inconvenience that the electron discharge is localized at the level of the winding whereby only a fraction of the cathode cylinder surface is efi'ectively utilized for the emission; thus the current of the diode is limited and consequently also the output power thereof.

In order to remedy this detect, it had been tried, as described in the French Patent No. 15,675 of May 4, 1965, filed by the assignee of the present application, to replace the winding by a set of ferromagnetic rings that surround the cathode cylinder and form pole pieces of a magnet structure in which the successive rings have alternately reversed polarities. In this manner a desired inhomogeneous distribution of the magnetic field was produced in the interelectrode space with an axial component of alternately reversed directions.

It might seem that with this system the whole of the cathode cylinder surface should participate in the emission and that the inconvenience of the preceding system would be eliminated. However, experience has shown that such is not the case and that the discharge is localized at the level of one or more spaces between two successive pole pieces, whereby the cathode is again insufiiciently utilized, exactly like in the known system. This phenomenon should probably be ascribed to the inhomogeneities of manufacture in the cathode surface as well as in the magnet system wherein the intensity may vary from one magnet to another.

The present invention has for its object a magnetic sys tem that allows to extend the discharge over the entireinterelectrode space and to utilize substantially the whole of the cathode surface.

The magnetic system in accordance wi.h the invention produces in the interelectrode space an inhomogeneous distribution of the magnetic field with an azimuthal component of periodically alternate directions.

The system of the present invention comprises a pair of pole pieces associated with a set of magnets which confer onto them opposite polarities, each pole piece having the shape of a rim provided with periodically spaced digits mutually intercalated like an interdigital line, surrounding the cathode cylinder.

The invention willbe best understood from the following description of the accompanying drawings in which:

FIGURES 1 and 2 are, respectively, an axial cross section and a transverse cross section of a diode provided with a magnetic circuit in accordance with the invention;

FIGURE 3 is a perspective view of the magnetic circuit; and

FIGURE 4 represents the same circuit in a developed view and indicates the trajectories followed by the electrons.

Referring now to the drawing wherein like reference numerals are used throughout the various view to designate like parts, and more particularly to FIGURES l and 2, there are represented in these figures two electrodes 1 and 2 which function, respectively, as an anode and a cathode of a diode whose air-tight envelope is completed by discs 3 and 7. Disc 3 supports the anode connection 4 tightly sealed to the glass base 5 which is also connected to the ring-shaped cathode connection 6. Disc 7 comprises the exhausting stem 8. The space comprised between electrodes 1 and 2 in the air-tight envelope is filled with an ionizable gas at an appropriate pressure.

A radial electric field is established in the interelectrode space by applying between connections 4 and 6 a direct current voltage, and a magnetic field is produced by means of a magnetic circuit in accordance with the present invention.

This circuit, shown in perspective view in FIGURE 3, comprises two rims 11 and 12 each provided with digits such as 13 and 14, respectively, which digits extend along the generatrices of the cathode cylinder 2 (FIG. 1) and intercalate with each other in the manner of interdigital delay lines. The two rims and the digits are made of a magnetically soft material and fixed together into a rigid assembly with the aid of non-magnetic struts 15. Rims 11 and 12 are given N and S polarities, respectively by digits 13 and In with the aid of a set of horse-shoeshaped magnets 16 in staggered arrangement on adjacent digits. Some of these magnets are shown in FIGURE 3.

This device operates as follows:

The operation of the tube itself and the rectifying effect obtained therein will not be described in detail since they have been already analyzed, for example, in the U.S.A. Patent 3,215,893 to G. Boucher and M. Soulet. It sufiices to recall that the electrons issued from the electrode that functions as a cathode follow within the interelectrode space trajectories or paths very much lengthened during one alternance or half-cycle of the alternating voltage. These trajectori s or paths are essentially perpendicular both to the magnetic and to the electric field.

In the device in accordance with the present invention, the magnetic field has an azimuthal component of periodically alternate directions, as indicated by the lines of force 17 in FIGURE 2; moreover, the intensity of this component increases towards the cathode surface, like in the prior art devices. The direction normal both to the radial electric field and to the azimuthal magnetic field is parallel to the generatrix of the cathode cylinder. Consequently, the electrons issued from cathode cylinder 2 follow first the direction of a generatrix as indicated by the path 18 in FIGURE 4 which represents in a developed view the circuit of FIGURE 3 with the superposition of the electron trajectory. Upon arrival at either rim 11 or 12 the electrons meet a zone about the extremities of digits 13 or 14 Where the magnetic lines of force no longer are contained in planes perpendicular to these digits and where the distribution of these lines of force exhibit an axial component at 19. The electron trajectory then is incurved so as to remain perpendicular to the magnetic lines of force and the electrons turn back along a generatrix in the reversed direction. The trajectory 18 is therefore a meander which, nevertheless, gradually approaches the anode 1 so that the projection thereof onto the plane perpendicular to the axis is a spiral 20 as indicated in FIGURE 2.

This operation results in two important advantages:

(a) The trajectory or path 18 undergoes a very important lengthening as compared to the trajectory followed by the electrons during the second alternance of the alternating voltage, and this lengthening provides all the advantages connected to a better ionization of the gas in the tube, improvement of the rectifying effect, etc.

(b) Since the magnetic circuit comprises but one pair of pole pieces, the trajectory started in the tube is a single one and it is joined by all the electrons issued from substaritially all the points of the cathode surface. The discharge then extends over the whole interelectrode space and the cathode surface is substantially totally utilized. Thus the inconvenience of the prior art system is eliminated;

While I have shown and described one embodiment in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to those skilled in the art, and I therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

1. A cylindrical magnetic structure for producing an inhomogeneous magnetic field in a substantially cylindrical, gas-filled, cross-field diode tube having an axial anode electrode and a cylindrical cathode electrode surrounding said anode, said magnetic structure comprising two circular rims surrounding said tube near the two extremities thereof, two sets of manually intercalated digits extending substantially parallelly to the axis of said tube and connected to said two rims, respectively, said rims and digits being made of a magnetically soft material,

and a number of small horse-shoe-shaped magnets attached by their extremities between each pair of adjacent digits with alternately reversed polarities from one digit to the other.

2. A diode discharge device of the crossed field type, comprising anode electrode means, cathode electrode means surrounding said anode electrode means, and means for producing a non-homogeneous magnetic field within the interelectrode space defined by said anode and cathode means including magnetic structure means defining a meander like path for the electrons emitted by said cathode means having to and fro path portions interconnected by reversing path portions and further means for producing in the to and fro path portions a magnetic field having an azimuthal component of periodically alternate directions with the intensity thereof increasing toward the cathode surface and for producing Within the reversing path portions a magnetic field of such configuration that the electrons continue to move in a predetermined direction to the next path portion.

3. The diode discharge device according to claim 2, wherein said magnetic structure means includes a magnetic circuit of interdigital-like configuration.

4. The diode discharge device according to claim 3, wherein said further means includes magnet means in staggered arrangement on adjacent digits of the interdigital-like circuit.

References Cited UNITED STATES PATENTS 3,084,279 4/1963 Osepchuk 313-156 x 3,215,893 11/1965 Boucher a a1. 313-156 x JAMES W. LAWRENCE, Primary Examiner.

S. A. SCHNEEBERGER, Assistant Examiner. 

2. A DIODE DISCHARGE DEVICE OF THE CROSSED FIELD TYPE, COMPRISING ANODE ELECTRODE MEANS, CATHODE ELECTRODE MEANS SURROUNDING SAID ANODE ELECTRODE MEANS, AND MEANS FOR PRODUCING A NON-HOMOGENEOUS MAGNETIC FIELD WITHIN THE INTERELECTRODE SPACE DEFINED BY SAID ANODE AND CATHODE MEANS INCLUDING MAGNETIC STRUCTURE MEANS DEFINING A MEANDER LIKE PATH FOR THE ELECTRONS EMITTED BY SAID CATHODE MEANS HAVING TO AND FRO PATH PORTIONS INTERCONNECTED BY REVERSING PATH PORTIONS AND FURTHER MEANS FOR PRODUCING IN THE TO AND FRO PATH PORTIONS A MAGNETIC FIELD HAVING AN AZIMUTHAL COMPONENT OF PERIODICALLY ALTERNATE DIRECTIONS WITH THE INTENSITY THEREOF INCREASING TOWARD THE CATHODE SURFACE AND FOR PRODUCING WITHIN THE REVERSING 